The present invention relates to a motor brake of a Diesel engine for a commercial vehicle, including a hydraulic mechanism that during the compression stroke, in the zone of the ignition-upper dead center position, holds the exhaust valve of the engine slightly open, with the hydraulic mechanism being formed by: an actuating cylinder that controls the exhaust valve and includes an actuating piston, a control line, and a transmitter cylinder that has a transmitter piston.
The so-called exhaust brake is known as a motor braking system. By closing a shutoff mechanism in the exhaust system, the exhaust work of the piston is increased bY building up a counterpressure in the exhaust manifold, with the piston having to exhaust against this counterpressure.
Motor brake systems are also known that make use of the compression work of the compression stroke, via discharge or exhaust in the zone of the ignition-upper dead center position, to effect braking (decompression braking). This is generally effected by a slight opening of the exhaust valve (however, it can also be effected via an additional small valve).
It is, of course, also possible to combine both brake systems.
The most frequently used decompression brake is the Jacobs brake. With this brake (preferably with engines having pump nozzles-injection systems) by placing a hydraulic unit on the cylinder head the pump stroke is utilized to slightly open the exhaust valve in the ignition-upper dead center position. The arrangement itself thus comprises a (separate) hydraulic system having a transmitter piston, and is driven by cams of the pump nozzle drive (or by the valve cams or push rods of the independent engine cylinder). The engine oil is used as hydraulic fluid. The opening and closing of the exhaust valve is controlled via electronic mechanisms and solenoid valves.
This additional hydraulic system forms a very complicated mechanism. In addition, it requires additional structural measures because of the housing, which contains the control mechanisms and the elements, and is placed upon the cylinder head. Thus, the drawback of this known motor brake is the expensive and complicated additional component.
It is therefore an object of the present invention to provide a decompression brake of the aforementioned general type that has a considerably more straightforward construction and is hence cheaper, in other words, a decompression brake that to the extent possible can be embodied without significant structural alteration. In addition, this decompression brake should be capable of being easily combined with the conventional exhaust brake.